vedant-z's blog

How to check if the upper_bound function on a sorted vector is pointing to end of the vector?
By vedant-z, history, 2 years ago, In English

If all the values in vector are less than or equal to M then "i" will point to v.end().

auto i = upper_bound(v.begin(), v.end(), M)- v.begin();

Now if I want to do certain action if "i" points to the end of vector, I tried

if(i == v.end()){ // Code }

But it doesn't work, throwing error: no match for ‘operator==’ (operand types are ‘long int’ and ‘std::vector::iterator’)

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2 years ago, # |
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You should just write auto i = upper_bound(v.begin(), v.end(), M). If you subtract v.begin() from it what you'll get will be the index corresponding to the iterator you wanted.

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2 years ago, # |
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Use auto i = upper_bound(v.begin(), v.end(), M); is a way mentioned above. In the statement i is a vector<int>::iterator.

And you can use if(i == v.size()){ // Code } too. Here v.size() is equal to v.end() - v.begin().

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2 years ago, # |
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auto iterator = upper_bound(v.begin(), v.end(), M);
if(iterator == v.end()){
     do_something();
}
int index = iterator - v.begin();
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2 years ago, # |
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define i as long long or int

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    2 years ago, # ^ |
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    if its pointing at end that means its the largest element of vector or what data structure you are using

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    2 years ago, # ^ |
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    int index = upper_bound(v.begin(), v.end(), M) - v.begin();
if(index == v.size()){
    do_something();
}

    Yeah, you can use another way but it doesn't matter int or auto is here.

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